SedNetNZ model expanded to include landslide erosion rates

A model for calculating landslide erosion rates for SedNetNZ.

Impact from erosion and landslides is familiar to most New Zealanders. Roads are closed, affecting travel and business, houses are lost and habitat is damaged. SedNetNZ provides land managers with tools to realistically simulate erosion processes and predict the impacts of future upstream land management scenarios on downstream water quality. It constructs sediment budgets for regional-scale river networks to identify patterns in the material fluxes. This can assist regional councils and land managers to target catchment and river management actions to improve water quality and habitat.

A paper on the model, co-authored by Manaaki Whenua – Landcare Research scientists Harley Betts, Les Basher, John Dymond, Alexander Herzig, Mike Marden and Chris Phillips, was published in Environmental Modelling & Software. The model uses the landslide probability for each slope class, slope class area, failure depth, soil bulk density, and sediment delivery ratio to calculate the mass of soil that will be eroded over a defined period. Landslide probability is derived from mapping a time series of landslides intersected with Digital Elevation Model-derived slopes. This approach works well for landslide modelling where rainfall-triggered shallow landslides occur – all too commonly in places such as the North Island hill country, and recently in areas closer to urban centres.